In addition to improving redness and hyperpigmentation/brown spots, IPL treatments improve texture, pore size and wrinkling. Those are not seen immediately after treatment, but take some time to develop,
The IPL treatments treat surface pigmentation and redness, but a part of the light spectrum reaches deeper into the dermis and stimulates collagen production. This in turn improves skin texture.
As for long term side effects, if there were no side effects immediately after the treatment, like a burn or a change in pigmentation, there should not be long term damage. IPL is made up of a spectrum of visible light, and unless you have a photosensitivity, that light is safe for the skin.